Intermittent Fasting and a No-Sugar Diet for Long COVID Symptoms

The Effect of a No-added Sugar Diet, Time-restricted Eating and Periodic Water Fasting on Long COVID Symptoms

This cross-over study will assess a no added sugar diet, a restricted daily eating window, and one or two full day water fasts to determine if there is an effect on self-reported symptoms of Long Covid (PASC).

Study Overview

• Status: Completed
• Conditions: Long COVID; Long Covid19
• Intervention / Treatment: Other: Low sugar diet and 10-12 hour eating window; Other: Low sugar diet, 8 hour eating window and fasting

Detailed Description

This remote study will use a cross-over design to test a diet change plus a 10-12 hour eating window (Treatment A) compared to a diet change, an 8-hour eating window, and one 36 or 60 hour fast per week (Treatment B). Both potential Treatment A and potential Treatment B are 4 weeks in duration. To be eligible, subjects must have a minimum of five common long COVID-19 symptoms. The fasting will limit food intake but not water intake. There will be a two-week run-in with weekly surveys of patient-reported symptoms and severity. The subjects will be randomly assigned to Group AB or to Group BA. Since the water fasts are at the beginning of the week (with symptoms surveyed at the end of the week) there is a 5-6 day washout and then a cross-over to the other treatment for Group BA. A Likert 0-4 scale is used to track the severity of 28 of the most common patient-reported symptoms each week. An additional 30 symptoms are also tracked. Subjects are asked to follow a no-added sugar diet for the entire 10 weeks of the study.

• Study Type: Interventional
• Enrollment (Actual): 77
• Phase: Not Applicable

Contacts and Locations

Study Locations

• United States
  • Colorado
    • Boulder, Colorado, United States, 80303
      • Remote trial - anyone residing in the United States
  • Washington
    • Yakima, Washington, United States, 98901
      • Pacific Northwest University

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria

• Adult (18-69 years old)
• Five or more common Long Covid symptoms
• Free from fever > 100F and known bacterial and parasitic infections
• Must indicate willingness to limit certain supplements and report all medications.
• Must indicate willingness to make significant dietary changes - and limit daily eating to an 8 or 10 hour window.
• Must indicate willingness to attempt 36 hr or 60 hr water fasts each week for 4 weeks.
• Have a valid email address and phone number
• Reside in the United States
• Be able to read and to communicate in English
• Must indicate willingness to avoid "extra" supplements such as Fish Yes Oil, Cod liver Oil, Krill Oil, MCT oil, Coconut Oil, Tumeric/Curcumin, Berberine, Quercetin (> 500 mg), Red Yeast Rice, French Marine Bark extract, Red Sage, Ginko biloba, Oregano Oil, Peppermint Oil, Black seed oil, Cinnamon bark extract, Elderberry, Stinging Nettle, Milk Thistle, Monolaurin, Vendicinals 9, Tollovid, QuadraMune and all Probiotics.
• Must indicate willingness to avoid certain nutraceuticals such as Zinc (more than 25 mg), Arginine, Glutamine, Palmitoylethanolamide (PEA), Alpha Lipoic Acid, L Carnitine and Taurine during the study period.
• Must indicate willingness to avoid longevity supplements such as NAD+, Niacin, NMN, Nicotinamide Riboside, Spermidine and Fisetin during the study period.
• Must indicate willingness to halt Olive oil consumption greater than 1 tsp daily during the study period.

Exclusion Criteria:

• Likely COVID-19 or SARS-CoV-2 infection < 45 days before enrollment
• Body Mass Index (BMI) must be 20 or greater
• Past history of an eating disorder.
• Previously fasted more than 18 hours with Long COVID
• Currently doing intermittent fasting
• Pregnant or breast-feeding
• Severe pulmonary disease requiring supplemental oxygen
• Partial loss of vision due to macular degeneration
• Any recent (90 days) history of malignancies, fractures, surgery, radiation, chemo, anesthesia, or traumas
• Diagnosed with Type I or Type II Diabetes
• Previous Autoimmune condition
• Heart condition (Coronary artery disease, Heart valve disease, Heart No failure, Stroke)
• Pre-pandemic Arrythmia
• Liver disease
• Previous Chronic Health Conditions that did not fully resolve (Includes ME/CFS, Lyme Disease, and Fibromyalgia)
• Prescription anticoagulation medication that cannot be halted during the study period. Brilinta (ticagrelor), Plavix (clopidogrel), Coumadin, Warfarin etc.
• High Cholesterol medications that cannot be halted or reduced during the study period (Fenofibrate, Statins > 10 mg)
• Anti-inflammatories or immunosuppressants such as Steroids, Low dose Naltrexone (LDN), Maraviroc, Remicade/Infliximab or Colchicine that cannot be halted during the study period
• Metformin, Ivermectin, or peptides such as BCP-157 that cannot be halted during the study period

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: Single

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: 10-12 hour daily Time-Restricted Eating (4 weeks); In this crossover trial, half the participants did the 10-hour TRE first (treatment A), half did it last. A no added sugar diet was suggested for the entire study.	Other: Low sugar diet and 10-12 hour eating window; Low sugar diet and 10-12 hour eating window for four weeks
Experimental: 8-hour TRE, weekly 23 to 60 hour fast (4 weeks); Eating in an 8-hour window daily, with one 23-60 hour fast per week. A no-added sugar diet was suggested.	Other: Low sugar diet, 8 hour eating window and fasting; Low sugar diet, 8 hour eating window and a 36-60 hour fast once per week for four weeks.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in LC-Score, Per Treatment	This Outcome Measure is calculated by subtracting the Long COVID symptom severity score (LC-Score) before a treatment from the LC-Score after the treatment (i.e., score-after minus score-before). Negative values represent a reduction in number and severity of symptoms following treatment. LC-Scores are the sum of severity scores (0-4) for 28 common symptoms plus the count of 32 additional symptoms present. The maximum possible LC-Score is (28x4)+32 = 144.	Before and after 4 weeks of Fasting treatment or TRE treatment
Change in Number of Long COVID Symptoms, Per Treatment	This Outcome Measure is calculated by subtracting the Number of Long COVID symptoms (numLCsym) before a treatment from the numLCsym after the treatment (i.e., number-after minus number-before). Negative values represent a reduction in number of symptoms following treatment. The numLCsym is the count of 60 common symptoms.	Before and after 4 weeks of Fasting treatment or TRE treatment

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in LC-Score, Overall	This Outcome Measure is calculated by subtracting the Long COVID symptom severity score (LC-Score) at baseline from the LC-Score after the final treatment (i.e., score-after minus score-before). Negative values represent a reduction in number and severity of symptoms following treatment. LC-Scores are the sum of severity scores (0-4) for 28 common symptoms plus the count of 32 additional symptoms present. The maximum possible LC-Score is (28x4)+32 = 144.	From enrollment to the end of the final treatment (10 weeks)
Change in Number of Long COVID Symptoms, Overall	This Outcome Measure is calculated by subtracting the Number of Long COVID symptoms (numLCsym) at baseline from the numLCsym after the final treatment (i.e., number-after minus number-before). Negative values represent a reduction in number of symptoms following treatment. The numLCsym is the count of 60 common symptoms.	From enrollment to the end of the final treatment (10 weeks)
Serious Adverse Events	Adverse events were medically reviewed and categorized as Serious if appropriate	During 4 weeks of Fasting treatment or during 6 weeks of TRE

Collaborators and Investigators

• Sponsor: Pacific Northwest University of Health Sciences
• Investigators: Principal Investigator: Jeffrey Novack, PhD, Pacific Northwest University of Health Sciences

Publications and helpful links

General Publications

• Bunker T, Horne BD, Baldwin MD, Sorrells R, Turner S, Laube L, Solomon A, Horne LA, Novack J. Intermittent fasting and a no-sugar diet for Long COVID symptoms: a randomized crossover trial. Sci Rep. 2025 Jul 29;15(1):27563. doi: 10.1038/s41598-025-07461-0.

Study record dates

Study Major Dates

• Study Start (Actual): November 4, 2022
• Primary Completion (Actual): July 1, 2024
• Study Completion (Actual): September 10, 2024

Study Registration Dates

• First Submitted: January 3, 2023
• First Submitted That Met QC Criteria: January 17, 2024
• First Posted (Actual): January 19, 2024

Study Record Updates

• Last Update Posted (Actual): May 14, 2026
• Last Update Submitted That Met QC Criteria: April 22, 2026
• Last Verified: April 1, 2026

More Information

Terms related to this study

• Keywords: diet; COVID-19; fasting
• Additional Relevant MeSH Terms: Post-Infectious Disorders; Pathologic Processes; Chronic Disease; Disease Attributes; Respiratory Tract Infections; Infections; RNA Virus Infections; Virus Diseases; Respiratory Tract Diseases; Lung Diseases; Pneumonia, Viral; Pneumonia; Coronavirus Infections; Coronaviridae Infections; Nidovirales Infections; Pathological Conditions, Signs and Symptoms; Behavior; Feeding Behavior; COVID-19; Post-Acute COVID-19 Syndrome; Fasting
• Other Study ID Numbers: 2022-06-PNWU

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: No current plan to share data with other researchers.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No